The present invention relates in general to a dental hand tool used for trimming restorative material which is used as a filling in dental work. The tool of this invention is particularly adapted for use for trimming more modern filling material such as composite resin dental materials. The trimming tool of this invention is for removing excess restorative material so as to more perfectly contour the restorative material to match the natural crown or contour of the original surface. The trimming in accordance with the invention is accomplished by a novel shaving blade construction, preferably of a hardened material, such as tungsten carbide, which avoids the staining of more modern filling materials such as composite resin restorative materials.
In restorative dentistry, especially when using cosmetic (white) filling or crown material, the trimming step is performed so as to preserve and enhance the cosmetic appearance of the restoration. Typically, this step involves removing excess restorative material so that there is a smooth matching contour between the restorative material in the filled cavity and the original tooth surface. Also, it is important to have a smooth transition between the tooth surface and the restorative material without the presence of any abrupt joint.
A common technique for shaping the restorative material involves the use of a rotary instrument such as a rotary burr which essentially grinds the hardened restorative material by an abrasive action. However, this technique is dangerous because there is a chance of destroying the hard tooth substance. Also, the composite resin dental restorative material sets to a hardened shatterable state, so that it is like glass and somewhat brittle and, therefore, the vibration caused by the use of a burr instrument may cause small fragments of the material to shatter particularly at the margins, thus creating small voids. In consequence, as is known, vibration from a burr or other rotary tool can cause iatrogenic damage. These small voids or cracks are a problem as they may be an annoyance to the patient, and also can fill with plaque or other undesirable substances which can damage the host tooth and shorten the life of the restoration.
Existing dental instruments do not use a carbide tip. Carbide has been employed primarily in constructing chisels and the like instruments, where hardness is required but this material has not been used in construction of dental hand-tools used in dental restoration for the shaping of restorative material. However, it is an object of this invention to provide a dental trimmer having at least the blade edge of a hardened material such as tungsten carbide. This material is also advantageous in that it prevents staining of the restorative material. If the restorative material is of a cosmetic nature such as the composite resins with which this invention is concerned, the tool that is used should not stain or otherwise contaminate the filling material. Generally, this rules out tools that are constructed of ferrous material.
The following prior art patents show bladed instruments: U.S. Pat. Nos. 940,351; 1,605,322; 2,634,499; and 4,060,897. The Bates U.S. Pat. No. 1,605,322 shows a pyorrhea curette which is more of a surgical instrument for cutting soft tissue or cleaning out debris and granulation tissue. This instrument is not adapted especially in its shape for contouring restorative material used in dental restoration. This prior art instrument is primarily for use beneath the gum line whereas the instrument in accordance with the present invention is primarily for use above the gum line.
The Greenstein U.S. Pat. No. 4,060,897 is not an instrument that is for use in the mouth but is used in making a dental restoration by a vibration technique where the restoration is to be fired in an oven and is primarily constructed of a ceramic porcelain. Furthermore, the structure shown in this prior art patent again is not adapted especially in its configuration for use in shaving restorative material which is used as a filling in an existing tooth surface.